NOTIFICATION OF DISASTER CONDITION AND ALTERNATIVE PLMNs

ABSTRACT

Systems and methods for enabling notification of disaster conditions and alternative Public Land Mobile Networks (PLMNs) to network nodes are disclosed. In one embodiment, a method performed by a User Equipment (UE) for responding to a disaster condition in a first PLMN, comprises determining that a first PLMN is not available; determining that a second PLMN is available for disaster roaming; and attempting to register with the second PLMN, responsive to determining that the first PLMN is not available due to the disaster condition and determining that a second PLMN is available for disaster roaming. In this way, a UE is informed of the failure of its currently used PLMN due to a disaster condition and a service may be provided in another PLMN, where the UE under normal conditions may not be allowed to receive a service from the second PLMN.

RELATED APPLICATIONS

This application claims the benefit of provisional patent applicationSer. No. 63/110,215, filed Nov. 5, 2020, the disclosure of which ishereby incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to enabling notification of disasterconditions, e.g. earthquake, tsunami, or landslide, in a first PublicLand Mobile Network (PLMN) and an alternative PLMN to network nodes anda User Equipment (UE).

BACKGROUND

High availability of the Fifth Generation (5G) system has been discussedin Third Generation Partnership Project (3GPP), and it has been decidedto perform a study to seek solutions to minimize service interruption incase of disaster conditions impacting a Public Land Mobile Network(PLMN). Solutions that enable User Equipments (UEs) using a PLMN failingservice due to disaster condition to receive service using alternativePLMNs are to be studied. In this regard, at 3GPP TSG-CT WG1 Meeting#126-e (Electronic meeting; 15-23 Oct. 2020), the following documentswere submitted: (1) “MINT: solutions for all key issues”; (2) “MINT:alternative 2 for How do other PLMNs indicate that they can accept‘Disaster Inbound Roamers’?”; (3) “MINT: solution for How canUE/subscribers perform network selection for disaster roaming?”; (4)“MINT: alternative 1 for How do other PLMNs indicate that they canaccept ‘Disaster Inbound Roamers’?”; and (5) “MINT: solution for How areUEs/subscribers 5 notified that a ‘Disaster Condition’ applies?” Theintention of the study is to identify solutions that can be introducedin the 3GPP standard. Thus, there are no existing solutions for the usecases of the study in the current baseline 3GPP 5G system.

SUMMARY

Embodiments of enabling notification of disaster conditions andalternative Public Land Mobile Networks (PLMNs) to network nodes aredisclosed. In one embodiment, a method performed by a User Equipment(UE) for responding to a disaster condition in a first PLMN, comprisesdetermining that a first PLMN is not available due to a disastercondition; determining that a second PLMN is available for disasterroaming; and attempting to register with the second PLMN, responsive todetermining that the first PLMN is not available due to the disastercondition and determining that a second PLMN is available for disasterroaming. In this way, a UE is informed of the failure of its currentlyused PLMN due to a disaster condition and a service may be provided inanother PLMN, where the UE under normal conditions may not be allowed toreceive a service from the another PLMN.

In one embodiment, the method further comprises receiving a disasterroaming PLMN list from the second PLMN. The disaster roaming PLMN listcomprises a PLMN Identifier (ID) of the first PLMN.

In one embodiment, receiving the disaster roaming PLMN list comprisesreceiving the disaster roaming PLMN list in a broadcast on a cell in thesecond PLMN (PLMN X).

In one embodiment, receiving the disaster roaming PLMN list comprisesreceiving the disaster roaming PLMN list in a public warning system(PWS) message from a cell in the second PLMN.

In one embodiment, determining that the second PLMN is available fordisaster roaming comprises determining that the second PLMN is availablefor disaster roaming based on the disaster roaming PLMN list.

In one embodiment, determining that the first PLMN is not available dueto the disaster condition comprises: determining that there is noavailable cell of the first PLMN (PLMN Y) and determining that a PLMNIdentifier (ID) of the first PLMN is comprised in the disaster roamingPLMN list.

In one embodiment, determining that the first PLMN is not available dueto the disaster condition comprises: transmitting a registration requestto the first PLMN; not receiving a response to the registration request;and determining that a PLMN Identifier, ID, of the first PLMN iscomprised in the disaster roaming PLMN list.

In one embodiment, determining that the first PLMN is not available dueto a disaster condition comprises transmitting a registration request tothe first PLMN and receiving a rejection of the registration requestcomprising an indication of the disaster condition.

In one embodiment, determining that the first PLMN is not available dueto the disaster condition comprises transmitting a service request tothe first PLMN; not receiving a response to the service request; anddetermining that a PLMN Identifier (ID) of the first PLMN is comprisedin the disaster roaming PLMN list.

In one embodiment, determining that the first PLMN is not available dueto the disaster condition comprises transmitting a service request tothe first PLMN and receiving a rejection of the service requestcomprising an indication of the disaster condition.

In one embodiment, determining that the first PLMN is not available dueto the disaster condition comprises camping on a cell of the first PLMNand receiving a broadcast on the cell that comprises information thatindicates that a disaster condition exists on the first PLMN.

In one embodiment, determining that the first PLMN is not available dueto a disaster condition comprises transmitting a registration request tothe first PLMN and receiving a registration reject from the first PLMNincluding a message of Fifth Generation System Mobility Management(SGMM) #XXX disaster condition identified.

In one embodiment, determining that the first PLMN is not available dueto the disaster condition comprises transmitting a service request tothe first PLMN and receiving a service reject from the first PLMNincluding a message of Fifth System Mobility Management (SGMM) #XXXdisaster condition identified.

In one embodiment, the UE is not otherwise permitted to use the secondPLMN.

Corresponding embodiment of a UE is also disclosed. A UE comprises oneor more transmitters, one or more receivers and processing circuitryassociated with the one or more transmitters and the one or morereceivers. The processing circuitry is configured to cause the UE todetermine that a first PLMN is not available due to a disastercondition, determine that a second PLMN is available for disasterroaming, and attempt to register with the second PLMN, responsive todetermining that the first PLMN is not available due to the disastercondition and determining that a second PLMN is available for disasterroaming.

Corresponding embodiments of a Radio Access Network (RAN) node andmethods performed by the RAN node are also disclosed.

In one embodiment, a method performed by a Radio Access Network (RAN)node of a second PLMN, comprises transmitting disaster roaming PLMN listcomprising a PLMN Identifier (ID) of a first PLMN for which the secondPLMN is available to provide a disaster roaming.

In one embodiment, transmitting the disaster roaming PLMN list comprises

broadcasting information comprising the disaster roaming list in acorresponding cell of the second PLMN.

In one embodiment, transmitting the disaster roaming PLMN list comprisesbroadcasting a Public Warning System (PWS) message comprising thedisaster roaming PLMN list in a corresponding cell of the second PLMN.

In one embodiment, the PWS message further comprises a messageidentifier that is set to a value that indicates that the second PLMN isavailable for the disaster roaming.

In one embodiment, the method further comprises receiving a registrationrequest from a UE that desires to use the second PLMN for the disasterroaming and processing the registration request such that the UE isallowed to use the second PLMN.

In one embodiment, a RAN node is adapted to transmit a disaster roamingPLMN list comprising a PLMN Identifier (ID) of a first PLMN for which asecond PLMN is available to provide a disaster roaming.

In one embodiment, a RAN node comprising processing circuitry configuredto cause the RAN node to transmit a disaster roaming PLMN listcomprising a PLMN Identifier (ID) of a first PLMN for which a secondPLMN is available to provide a disaster roaming.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawing figures incorporated in and forming a part ofthis specification illustrate several aspects of the disclosure, andtogether with the description serve to explain the principles of thedisclosure.

FIG. 1 illustrates one example of a cellular communications system inaccordance with the embodiments in the present disclosure.

FIG. 2 illustrates a wireless communication system represented as aFifth Generation (5G) network architecture composed of core NetworkFunctions (NFs), where interaction between any two NFs is represented bya point-to-point reference point/interface.

FIG. 3 illustrates a 5G network architecture using service-basedinterfaces between the NFs in the Control Panel (CP).

FIG. 4 illustrates the first solution of the present disclosure.

FIG. 5 illustrates a flow chart of the first solution.

FIG. 6 illustrates the second solution of the present disclosure.

FIG. 7 illustrates a flow chart of the second solution.

FIG. 8 illustrates a schematic block diagram of a network node accordingto some embodiments of the present disclosure.

FIG. 9 illustrates a schematic block diagram that illustrates avirtualized embodiment of a network node according to some embodimentsof the present disclosure.

FIG. 10 illustrates a schematic block diagram of a network nodeaccording to some embodiments of the present disclosure.

FIG. 11 illustrates a schematic block diagram of a wirelesscommunication device according to some embodiments of the presentdisclosure.

FIG. 12 illustrates a schematic block diagram of the wirelesscommunication device according to some embodiments of the presentdisclosure.

DETAILED DESCRIPTION

The embodiments set forth below represent information to enable thoseskilled in the art to practice the embodiments and illustrate the bestmode of practicing the embodiments. Upon reading the followingdescription in light of the accompanying drawing figures, those skilledin the art will understand the concepts of the disclosure and willrecognize applications of these concepts not particularly addressedherein. It should be understood that these concepts and applicationsfall within the scope of the disclosure.

Radio Node: As used herein, a “radio node” is either a radio access nodeor a wireless communication device.

Radio Access Node: As used herein, a “radio access node” or “radionetwork node” or “radio access network node” is any node in a RadioAccess Network (RAN) of a cellular communications network that operatesto wirelessly transmit and/or receive signals. Some examples of a radioaccess node include, but are not limited to, a base station (e.g., a NewRadio (NR) base station (gNB) in a Third Generation Partnership Project(3GPP) Fifth Generation (5G) NR network or an enhanced or evolved Node B(eNB) in a 3GPP Long Term Evolution (LTE) network), a high-power ormacro base station, a low-power base station (e.g., a micro basestation, a pico base station, a home eNB, or the like), a relay node, anetwork node that implements part of the functionality of a base station(e.g., a network node that implements a gNB Central Unit (gNB-CU) or anetwork node that implements a gNB Distributed Unit (gNB-DU)) or anetwork node that implements part of the functionality of some othertype of radio access node.

Core Network Node: As used herein, a “core network node” is any type ofnode in a core network or any node that implements a core networkfunction. Some examples of a core network node include, e.g., a MobilityManagement Entity (MME), a Packet Data Network Gateway (P-GW), a ServiceCapability Exposure Function (SCEF), a Home Subscriber Server (HSS), orthe like. Some other examples of a core network node include a nodeimplementing an Access and Mobility Management Function (AMF), a UserPlane Function (UPF), a Session Management Function (SMF), anAuthentication Server Function (AUSF), a Network Slice SelectionFunction (NSSF), a Network Exposure Function (NEF), a Network Function(NF) Repository Function (NRF), a Policy Control Function (PCF), aUnified Data Management (UDM), or the like.

Communication Device: As used herein, a “communication device” is anytype of device that has access to an access network. Some examples of acommunication device include, but are not limited to: mobile phone,smart phone, sensor device, meter, vehicle, household appliance, medicalappliance, media player, camera, or any type of consumer electronic, forinstance, but not limited to, a television, radio, lighting arrangement,tablet computer, laptop, or Personal Computer (PC). The communicationdevice may be a portable, hand-held, computer-comprised, orvehicle-mounted mobile device, enabled to communicate voice and/or datavia a wireless or wireline connection.

Wireless Communication Device: One type of communication device is awireless communication device, which may be any type of wireless devicethat has access to (i.e., is served by) a wireless network (e.g., acellular network). Some examples of a wireless communication deviceinclude, but are not limited to: a UE in a 3GPP network, a Machine TypeCommunication (MTC) device, and an Internet of Things (IoT) device. Suchwireless communication devices may be, or may be integrated into, amobile phone, smart phone, sensor device, meter, vehicle, householdappliance, medical appliance, media player, camera, or any type ofconsumer electronic, for instance, but not limited to, a television,radio, lighting arrangement, tablet computer, laptop, or PC. Thewireless communication device may be a portable, hand-held,computer-comprised, or vehicle-mounted mobile device, enabled tocommunicate voice and/or data via a wireless connection.

Network Node: As used herein, a “network node” is any node that iseither part of the RAN or the core network of a cellular communicationsnetwork/system.

Note that the description given herein focuses on a 3GPP cellularcommunications system and, as such, 3GPP terminology or terminologysimilar to 3GPP terminology is oftentimes used. However, the conceptsdisclosed herein are not limited to a 3GPP system.

Note that, in the description herein, reference may be made to the term“cell”; however, particularly with respect to 5G NR concepts, beams maybe used instead of cells and, as such, it is important to note that theconcepts described herein are equally applicable to both cells andbeams.

There currently exist certain challenge(s). In the above-describeddocument titled “MINT: solutions for all key issues,” the following keyissues were identified:

-   -   Key Issue #1: How are subscribers Notified that a “Disaster        Condition” applies?    -   Key Issue #3: How do other PLMNs (those not subject to the        disaster) indicate that they can accept “Disaster Inbound        Roamers”?        The current Fifth Generation (5G) system does not support any        mechanisms for the above Key Issue #1 and Key Issue #3, and        enhancements are needed to introduce mechanisms to solve these        key issues.

Certain aspects of the present disclosure and the embodiments describedherein may provide solutions to the aforementioned or other challenges.In a first solution for the above Key Issues (“Key Issue #1” and “KeyIssue #3”), a UE using a certain PLMN (hereinafter “PLMN Y”), which maybe e.g. the UE's Home PLMN (HPLMN), is made aware of the failure of aPLMN Y due to a disaster condition by:

-   -   the UE determining that there is no available cell of the PLMN        Y, combined with broadcasting, by an available cell of another        PLMN X, the PLMN ID of the PLMN Y in a “disaster roaming PLMN        list”;    -   the UE camping on a cell of the PLMN Y that broadcasts a        “disaster condition identified” message; or    -   the UE determining that PLMN Y's core network is impacted by a        disaster by:        -   a registration procedure or a service request procedure in            the PLMN Y failing with no response, combined with            broadcasting, by an available cell of another PLMN X, the            PLMN ID of the PLMN Y in the “disaster roaming PLMN list”;            or        -   a registration procedure or a service request procedure in            the PLMN Y being rejected with a message of “SGMM cause #XXX            ‘disaster condition identified”;            and the UE determines that another PLMN (hereinafter “PLMN            X”) is available for a disaster roaming (i.e., a roaming            while the PLMN Y has the disaster condition) if:    -   the UE receives broadcasting, by an available cell of another        PLMN X, the PLMN ID of the PLMN Y in the “disaster roaming PLMN        list”; and    -   the PLMN X is in UE's list of forbidden PLMNs.

In one embodiment of the first solution, the UE using a serving PLMN(PLMN Y), which may be for example the HPLMN of the UE, determines thatthe serving PLMN Y has a disaster condition if:

-   -   no PLMN Y cell is available to the UE and the UE receives, from        a radio access node (e.g., base station) serving a cell of the        PLMN X (which is outside the UE's serving PLMN Y), a broadcast        of a “disaster roaming PLMN list” including the PLMN ID of PLMN        Y;    -   the UE camping on a cell of the PLMN Y that broadcasts a message        of “disaster condition identified”; or    -   the UE determines that the core network of the PLMN Y is        impacted by the disaster by:        -   a registration procedure or a service request procedure in            the PLMN Y failing with no response and the UE receives,            from a radio access node (e.g., base station) serving a cell            of PLMN X (which is outside the UE's serving PLMN Y), a            broadcast of a “disaster roaming PLMN list” including the            PLMN ID of PLMN Y; or        -   a registration procedure or a service request procedure in            the PLMN Y being rejected with a message of “5GMM cause #XXX            ‘disaster condition identified”.            and the UE determines that another PLMN (PLMN X) is            available for the disaster roaming (i.e., roaming while PLMN            Y has the disaster condition) if:    -   the UE receives, from a radio access node (e.g., base station)        serving a cell of PLMN X (which is outside the UE's serving PLMN        Y), a broadcast of the “disaster roaming PLMN list” including        the PLMN ID of PLMN Y; and    -   the PLMN X is in UE's list of forbidden PLMNs.

In a second solution for the above Key Issues (“Key Issue #1” and “KeyIssue #3”), a UE using a certain PLMN C′PLMN Y″), which may be e.g., aHPLMN of the UE, is made aware of the failure of the serving PLMN due toa disaster condition by:

-   -   the UE determining there is no available cell of the PLMN Y        combined with a cell of another PLMN (“PLMN X”) broadcasting a        Public Warning System (PWS) message:        -   with a message identifier set to the            disaster-roaming-possible value; and        -   with the content of the PWS message containing the “disaster            roaming PLMN list” including the PLMN ID of the PLMN Y;    -   the UE camping on a cell of the PLMN Y that broadcasts a message        of “disaster condition identified”; or    -   the UE determining that the PLMN Y's core network is impacted by        disaster by        -   a registration procedure or a service request procedure in            the PLMN Y failing with no response, combined with a cell of            another PLMN C′PLMN X″) broadcasting a PWS message:            -   with the message identifier set to the                disaster-roaming-possible value; and            -   with the content of the PWS message containing the                “disaster roaming PLMN list” including the PLMN ID of                the PLMN Y; or        -   a registration procedure or a service request procedure in            the PLMN Y being rejected with a message of “5GMM cause            #)00X disaster condition identified”’.            and the UE determines that another PLMN (“PLMN X”) is            available for a disaster roaming (i.e., roaming while PLMN Y            has the disaster condition) if:    -   the UE receives, from a radio access node (e.g., base station)        serving a cell of PLMN X (which is outside the UE's serving PLMN        Y), a broadcast of a PWS message,        -   with the message identifier set to the            disaster-roaming-possible value; and        -   with the content of the PWS message containing the “disaster            roaming PLMN list” including the PLMN ID of the PLMN Y; and    -   the PLMN X is in UE's list of forbidden PLMNs.

Via one of the above solutions, the UE registered to a PLMN maydetermine that this PLMN is unable to provide a service due to adisaster condition and may instead determine another PLMN that mayprovide a service.

Embodiments of the present disclosure introduce a “disaster roaming PLMNlist” provided by a PLMN that is capable of providing a service tosubscribers of another PLMN(s) impacted by disaster conditions. The PLMNproviding the disaster roaming is operational and may provide the“disaster roaming PLMN list.” Also, in case of complete outage of thefailing PLMN, its subscribers may deduce the disaster condition as thePLMN ID of UE's failing PLMN (which may be, e.g., the HPLMN of the UE)is included in the “disaster roaming PLMN list” received from the PLMNoffering the disaster roaming. The “disaster roaming PLMN list” isreceived without the need to register to the alternative PLMN, i.e.functionality is assured also in case the alternative PLMN normally isforbidden for the subscriber, and therefore access would not beattempted unless the disaster roaming is offered. Additionally, thebroadcasting of the “disaster condition identified” by an impacted PLMNmay assist in quicker determination of failing service by UEs registeredto the impacted PLMN.

Certain embodiments may provide one or more of the following technicaladvantage(s). One advantage to the proposed solutions is that a UE isinformed of the failure of its currently used PLMN due to a disastercondition and a service may be provided in another PLMN, where the UEunder normal conditions may not be allowed to receive a service from theanother PLMN.

FIG. 1 illustrates one example of a cellular communications system 100in which embodiments of the present disclosure may be implemented. Inthe embodiments described herein, the cellular communications system 100is a 5G system (5GS) including a Next Generation RAN (NG-RAN) and a 5GCore (5GC) or an Evolved Packet System (EPS) including an EvolvedUniversal Terrestrial RAN (E-UTRAN) and an Evolved Packet Core (EPC). Inthis example, the RAN includes base stations 102-1 and 102-2, which inthe 5GS include NR base stations (gNBs) and optionally next generationeNBs (ng-eNBs) (e.g., LTE RAN nodes connected to the 5GC) and in the EPSinclude eNBs, controlling corresponding (macro) cells 104-1 and 104-2.The base stations 102-1 and 102-2 are generally referred to hereincollectively as base stations 102 and individually as base station 102.Likewise, the (macro) cells 104-1 and 104-2 are generally referred toherein collectively as (macro) cells 104 and individually as (macro)cell 104. The RAN may also include a number of low power nodes 106-1through 106-4 controlling corresponding small cells 108-1 through 108-4.The low power nodes 106-1 through 106-4 can be small base stations (suchas pico or femto base stations) or Remote Radio Heads (RRHs), or thelike. Notably, while not illustrated, one or more of the small cells108-1 through 108-4 may alternatively be provided by the base stations102. The low power nodes 106-1 through 106-4 are generally referred toherein collectively as low power nodes 106 and individually as low powernode 106. Likewise, the small cells 108-1 through 108-4 are generallyreferred to herein collectively as small cells 108 and individually assmall cell 108. The cellular communications system 100 also includes acore network 110, which in the 5G System (5GS) is referred to as the Thebase stations 102 (and optionally the low power nodes 106) are connectedto the core network 110.

The base stations 102 and the low power nodes 106 provide service towireless communication devices 112-1 through 112-5 in the correspondingcells 104 and 108. The wireless communication devices 112-1 through112-5 are generally referred to herein collectively as wirelesscommunication devices 112 and individually as wireless communicationdevice 112. In the following description, the wireless communicationdevices 112 are oftentimes UEs, but the present disclosure is notlimited thereto. The wireless communication devices 112 are UEs in theexample embodiments described below and, as such, the wirelesscommunication devices 112 are sometimes referred to herein as UEs 112.

As illustrated in FIG. 1 , a Cell Broadcasting Entity (CBE) 114 and aCell Broadcast Center (CBC) 116 may be connected to the core network110. When disasters, e.g. earthquake, tsunami, or landslide, may occur,the CBE 114 notifies the CBC 116 of a warning message of the disasters.Then, the CBC 116 forwards the warning message to the core network 110.

FIG. 2 illustrates a wireless communication system represented as a 5Gnetwork architecture composed of core Network Functions (NFs), whereinteraction between any two NFs is represented by a point-to-pointreference point/interface. FIG. 2 can be viewed as one particularimplementation of the system 100 of FIG. 1 .

Seen from the access side the 5G network architecture shown in FIG. 2comprises a plurality of UEs 112 connected to either a RAN 102 or anAccess Network (AN) as well as an AMF 200. Typically, the R(AN) 102comprises base stations, e.g. such as eNBs or gNBs or similar. Seen fromthe core network side, the 5GC NFs shown in FIG. 2 include a NSSF 202,an AUSF 204, a UDM 206, the AMF 200, a SMF 208, a PCF 210, and anApplication Function (AF) 212.

Reference point representations of the 5G network architecture are usedto develop detailed call flows in the normative standardization. The N1reference point is defined to carry signaling between the UE 112 and AMF200. The reference points for connecting between the AN 102 and AMF 200and between the AN 102 and UPF 214 are defined as N2 and N3,respectively. There is a reference point, N11, between the AMF 200 andSMF 208, which implies that the SMF 208 is at least partly controlled bythe AMF 200. N4 is used by the SMF 208 and UPF 214 so that the UPF 214can be set using the control signal generated by the SMF 208, and theUPF 214 can report its state to the SMF 208. N9 is the reference pointfor the connection between different UPFs 214, and N14 is the referencepoint connecting between different AMFs 200, respectively. N15 and N7are defined since the PCF 210 applies policy to the AMF 200 and SMF 208,respectively. N12 is required for the AMF 200 to perform authenticationof the UE 112. N8 and N10 are defined because the subscription data ofthe UE 112 is required for the AMF 200 and SMF 208.

The 5GC network aims at separating User Plane (UP) and Control Plane(CP). The UP carries user traffic while the CP carries signaling in thenetwork. In FIG. 2 , the UPF 214 is in the UP and all other NFs, i.e.,the AMF 200, SMF 208, PCF 210, AF 212, NSSF 202, AUSF 204, and UDM 206,are in the CP. Separating the UP and CP guarantees each plane resourceto be scaled independently. It also allows UPFs to be deployedseparately from CP functions in a distributed fashion. In thisarchitecture, UPFs may be deployed very close to UEs to shorten theRound Trip Time (RTT) between UEs and data network for some applicationsrequiring low latency.

The core 5G network architecture is composed of modularized functions.For example, the AMF 200 and SMF 208 are independent functions in theCP. Separated AMF 200 and SMF 208 allow independent evolution andscaling. Other CP functions like the PCF 210 and AUSF 204 can beseparated as shown in FIG. 2 . Modularized function design enables the5GC network to support various services flexibly.

Each NF interacts with another NF directly. It is possible to useintermediate functions to route messages from one NF to another NF. Inthe CP, a set of interactions between two NFs is defined as service sothat its reuse is possible. This service enables support for modularity.The UP supports interactions such as forwarding operations betweendifferent UPFs.

FIG. 3 illustrates a 5G network architecture using service-basedinterfaces between the NFs in the CP, instead of the point-to-pointreference points/interfaces used in the 5G network architecture of FIG.2 . However, the NFs described above with reference to FIG. 2 correspondto the NFs shown in FIG. 3 . The service(s) etc. that a NF provides toother authorized NFs can be exposed to the authorized NFs through theservice-based interface. In FIG. 3 the service based interfaces areindicated by the letter “N” followed by the name of the NF, e.g. Namffor the service based interface of the AMF 200 and Nsmf for the servicebased interface of the SMF 208, etc. The NEF 300 and the NRF 302 in FIG.3 are not shown in FIG. 2 discussed above. However, it should beclarified that all NFs depicted in FIG. 2 can interact with the NEF 300and the NRF 302 of FIG. 3 as necessary, though not explicitly indicatedin FIG. 2 .

Some properties of the NFs shown in FIGS. 2 and 3 may be described inthe following manner. The AMF 200 provides UE-based authentication,authorization, mobility management, etc. A UE 112 even using multipleaccess technologies is basically connected to a single AMF 200 becausethe AMF 200 is independent of the access technologies. The SMF 208 isresponsible for session management and allocates Internet Protocol (IP)addresses to UEs. It also selects and controls the UPF 214 for datatransfer. If a UE 112 has multiple sessions, different SMFs 208 may beallocated to each session to manage them individually and possiblyprovide different functionalities per session. The AF 212 providesinformation on the packet flow to the PCF 210 responsible for policycontrol in order to support Quality of Service (QoS). Based on theinformation, the PCF 210 determines policies about mobility and sessionmanagement to make the AMF 200 and SMF 208 operate properly. The AUSF204 supports authentication function for UEs or similar and thus storesdata for authentication of UEs or similar while the UDM 206 storessubscription data of the UE 112. The Data Network (DN), not part of the5GC network, provides Internet access or operator services and similar.

An NF may be implemented either as a network element on a dedicatedhardware, as a software instance running on a dedicated hardware, or asa virtualized function instantiated on an appropriate platform, e.g., acloud infrastructure.

Methods for a UE to determine that a HPLMN Y has a disaster conditionand that another PLMN X is available to provide disaster roaming arediscussed with reference to the flow diagram in FIGS. 4 through 7 .FIGS. 4 and 5 relate to example embodiments of the first solutiondescribed briefly above and detailed below. FIGS. 6 and 7 relate toexample embodiments of the second solution described briefly above anddetailed below.

When a first PLMN (“PLMN X”) is informed that another PLMN (“PLMN Y”)has a disaster condition and the PLMN X is to provide disaster roaming,the PLMN X configures PLMN X's cells to broadcast a “disaster roamingPLMN list” including the PLMN ID of the PLMN Y. In one embodiment, theconfiguration is done using Operations and Access Management (O&AM).

In one embodiment of the first solution, the UE determines that itsHPLMN Y has the disaster condition and that the PLMN X is available forthe disaster roaming if:

-   -   there is no available cell of the PLMN Y and an available cell        of the PLMN X broadcasts the PLMN ID of HPLMN Y in the “disaster        roaming PLMN list”; or    -   the UE camps on a cell of the PLMN Y that broadcasts a message        of “disaster condition identified”; or    -   the UE determines that the PLMN Y's core network is impacted by        a disaster by        -   a registration procedure or a service request procedure in            the PLMN Y failing with no response and an available cell of            the PLMN X broadcasts the PLMN ID of HPLMN Y in the            “disaster roaming PLMN list”; or        -   a registration procedure or a service request procedure in            the PLMN Y being rejected with a message of “5GMM cause            #)00X disaster condition identified'”.

In one embodiment, the UE determines that the PLMN Y's core network isimpacted by a disaster e.g.:

-   -   when a registration procedure or a service request procedure in        the PLMN Y fails due to expiration of the timer T3510 or T3517,        lower layer failure or a release of Non-Access Stratum (NAS)        signaling connection, and the registration attempt counter or        service request attempt counter is equal to 5 and an available        cell of the PLMN X broadcasts the PLMN ID of the PLMN Y in the        “disaster roaming PLMN list”; and/or    -   when a registration procedure or a service request procedure in        the PLMN Y is rejected with a message of “SGMM cause #XXX        ‘disaster condition identified”.

In one embodiment, the UE's determination that the PLMN Y has a“disaster condition” is cleared after timeout if determined by:

-   -   a registration procedure or a service request procedure in the        PLMN Y failing with no response and an available cell of PLMN X        broadcasts the PLMN ID of HPLMN Y in the “disaster roaming PLMN        list”; or    -   a registration procedure or a service request procedure in the        PLMN Y being rejected with a message of “5GMM cause #)00X        disaster condition identified’”.

FIG. 4 illustrates the operation of the UE 112 and various network nodes(e.g., the RAN node 102, the AMF 200) in accordance with one exampleembodiment of the first solution. The example embodiment of FIG. 4assumes that the PLMN X is informed about a disaster in the PLMN Y inthe area of the UE, the PLMN X is willing to provide a disaster roamingto UEs of the PLMN Y in the area, and the PLMN X sets up the RAN nodes102 of the PLMN X in the area to broadcast a “disaster roaming PLMNlist” including the PLMN ID of the PLMN Y. The procedure illustrated inFIG. 4 is as follows:

Step 400: The UE determines that UE's PLMN Y is not available (i.e., hasa disaster condition). In one embodiment, the UE 112 makes thisdetermination using one of the following alternatives A to D, whichAlternative A (step 400A): The UE 112 determines that there is noavailable cell of the PLMN Y and, as such, determines that the PLMN Yhas a disaster condition.

Alternative B (step 400B): The UE 112 camps on a cell of the PLMN Y thatbroadcasts a message of “disaster condition identified.” In other words,the UE 112 camps on a cell of the PLMN Y and receives a broadcast fromthat cell, which includes information indicating that the PLMN Y isexperiencing a disaster condition.

Alternative C (step 400C): The UE 112 attempts to perform a registrationprocedure or a service request procedure in the PLMN Y, and theregistration procedure or the service request procedure in the PLMN Yfails due to expiration of a timer (e.g., timer T3510 or T3517 in 3GPP),lower layer failure or release of NAS signaling connection, and theregistration attempt counter or service request attempt counter is equalto a predefined value (e.g., 5 in 3GPP).

Alternative-D (step 400D): The UE 112 determines that the PLMN Y isexperiencing a disaster condition if the registration procedure or theservice request procedure in the PLMN Y is rejected with a message of“SGMM cause #XXX ‘disaster condition identified”.

Alternatives A through D are alternatives or optional steps within Step1 for the UE to become aware that the PLMN Y is not available (i.e., isexperiencing a disaster condition).

Step 402: The UE 112 searches for other PLMNs and discovers a cell ofanother PLMN X that broadcasts a “disaster roaming PLMN list” includinga PLMN ID of the PLMN Y. In one embodiment, the UE 112 is not normallypermitted to use the PLMN X (e.g., PLMN X is in the forbidden PLMN listof the UE).

Step 404: Based on Steps 400 and 402, the UE 112 determines that thePLMN Y has a disaster condition and that the PLMN X is available for thedisaster roaming. Stated differently, in Alternative A and Alternative Cof Step 400, the UE 112 is unable to communicate with the PLMN Y butdoes not affirmatively learn that the PLMN Y is in a disaster conditionuntil receiving the “disaster roaming PLMN list” in Step 402. InAlternative B and Alternative D of Step 400, the UE 112 is affirmativelyinformed of the disaster condition in the PLMN Y. In all Alternatives ofStep 400, the UE 112 becomes aware that the PLMN X is available for thedisaster roaming for the UE 112 when the UE 112 receives the “disasterroaming PLMN list” in Step 402.

Step 406: As the UE 112 determined that the PLMN Y has the disastercondition and that the PLMN X is available for the disaster roaming, theUE 112 attempts to register with the PLMN X. In one embodiment, this isdone despite the fact that the UE 112 is otherwise not able to use thePLMN X (e.g., the PLMN X is in a forbidden PLMN list of the UE 112). Inone embodiment, the UE 112 attempts to register with the PLMN X only ifthere is no other PLMN that is available and allowable usingnon-disaster roaming.

FIG. 5 illustrates a method performed by a network node (e.g., the RANnode 102 and the AMF 200) in the PLMN X referred to in FIG. 4 . Themethod in FIG. 5 includes the following steps:

-   -   Step 500: Receiving, in a first PLMN (PLMN X), information about        a disaster condition in a second PLMN (PLMN Y) in an area of a        UE;    -   Step 502: Determining, in the first PLMN, a willingness to        provide a disaster roaming to UEs 112 of the second PLMN in the        area; and    -   Step 504: Setting up RAN nodes (e.g., base stations 102) in the        first PLMN to broadcast a “disaster roaming PLMN list” including        a PLMN ID of the second PLMN.

When the CBE 114 is informed that the PLMN Y has a disaster conditionand the CBE 114 decides to provide the disaster roaming for UEs 112(registered at the PLMN Y) in the PLMN X, the CBE 114 will trigger theCBC 116 to broadcast a PWS message in the PLMN X. The PWS messagecomprises (a) a message Identifier that is set to a newly reserveddisaster-roaming-possible value; and (b) PWS message content, whichcontains the “disaster roaming PLMN list,” including the PLMN ID of thePLMN Y.

The UE 112 determines that its PLMN Y (which may be its HPLMN) has adisaster condition if:

-   -   the UE 112 determines that there is no available cell of the        PLMN Y and an available cell of another PLMN X broadcasts a PWS        message, which includes (a) a message Identifier that is set to        a newly reserved disaster-roaming-possible value; and (b) PWS        message content, which contains the “disaster roaming PLMN        list,” including the PLMN ID of the PLMN Y, or    -   the UE 112 camps on a cell of the PLMN Y that broadcasts a        message of “disaster condition identified”; or    -   the UE 112 determines that the PLMN Y's core network is impacted        by a disaster by:        -   a registration procedure or a service request procedure in            the PLMN Y failing with no response and an available cell of            another PLMN X broadcasts the PWS message; or        -   a registration procedure or a service request procedure in            the PLMN Y being rejected with a message of “5GMM cause #>0X            disaster condition identified.”

In one embodiment, the UE 112 determines that the PLMN Y's core networkis impacted by a disaster e.g.:

-   -   when a registration procedure or a service request procedure in        the PLMN Y fails due to expiration of a timer (e.g., the timer        T3510 or T3517 in 3GPP), lower layer failure or release of NAS        signaling connection, and the registration attempt counter or        service request attempt counter is equal to 5 and an available        cell of another PLMN X broadcasts a PWS message:        -   with the Message Identifier set to the            disaster-roaming-possible value; and        -   with the content of the PWS message containing the “disaster            roaming PLMN list” including PLMN ID of PLMN Y; and/or    -   when a registration procedure or a service request procedure in        the PLMN Y is rejected with a message of “SGMM cause #XXX        ‘disaster condition identified.”

In one embodiment, the UE's determination that the PLMN Y's core networkhas the disaster condition is cleared after timeout if determined by:

-   -   a registration procedure or a service request procedure in the        PLMN Y failing with no response and an available cell of PLMN X        broadcasts the PWS message with the Message Identifier set to        the disaster-roaming-possible value; and    -   with the content of the PWS message containing the “disaster        roaming PLMN list” including PLMN ID of PLMN Y; and/or    -   a registration procedure or a service request procedure in the        PLMN Y being rejected with a message of “5GMM cause #>0X        disaster condition identified.”

FIG. 6 illustrates the operation of a UE 112 and a number of networknodes (e.g., the RAN node 102, AMF 200) in accordance with one exampleembodiment of the second solution. The example shown in FIG. 6 assumesthat the CBE 114 is informed about the disaster in the PLMN Y in area ofthe UE 112, decides that PLMN X is to provide disaster roaming to UEs112 of the PLMN Yin the area, and instructs the PLMN

X to send the PWS message comprising (a) a message Identifier that isset to a newly reserved disaster-roaming-possible value; and (b) PWSmessage content, which contains the “disaster roaming PLMN list,”including the PLMN ID of the PLMN Y.

In one embodiment, the CBE 114 instructs the PLMN X to send the PWSmessage using the flow for distribution of PWS messages in NG-RAN, asdescribed in FIG. 9.1 .3.5.2-1 of 3GPP TS 23.041 v17.0.0.

The procedure of FIG. 6 is as follows:

Step 1: The UE determines that the UE's PLMN Y (which may be its HPLMN)is not available using one of the following alternatives: Alternative A:The UE determines that there is no available cell of PLMN Y

and, as such, determines that PLMN Y has a disaster condition.

Alternative B: The UE camps on a cell of PLMN Y which broadcasts“disaster condition identified”. In other words, the UE camps on a cellof PLMN Y and receives a broadcast from that cell that includesinformation that indicates the PLMN Y is experiencing a disastercondition.

Alternative C: The UE attempts to perform registration or servicerequest procedure in PLMN Y and the registration or service requestprocedure in PLMN Y fails due to expiration of a timer (e.g., timerT3510 or T3517 in 3GPP), lower layer failure or release of NAS signalingconnection, and the registration attempt counter or service requestattempt counter is equal to a predefined value (e.g., 5).

Alternative D: The UE determines that PLMN Y is experiencing a disastercondition if registration or service request procedure in HPLMN Y isrejected with SGMM cause #XXX “disaster condition identified”.

Alternatives A through D are alternatives or optional steps within Step1 in which the UE becomes aware that the PLMN Y is not available (i.e.,is experiencing a disaster condition).

Step 2: The UE searches for other PLMNs and discovers a cell of anotherPLMN X via which a PWS message:

-   -   with the Message Identifier set to the disaster-roaming-possible        value; and    -   with the content of the PWS message containing the “disaster        roaming PLMN list” including PLMN ID of PLMN Y,        is broadcast. In one embodiment, the UE is not normally        permitted to use PLMN X (e.g., PLMN X is in forbidden PLMN list        of the UE).

Step 3: Based on Steps 1 and 2, the UE determines that PLMN Y has“disaster condition” and that the PLMN X is available for disasterroaming.

Stated differently, in Alternative A and Alternative C in Step 1, the UEis unable to communicate with the PLMN Y but does not affirmativelylearn that the PLMN Y is in a disaster condition until receiving thedisaster roaming PLMN list in Step 2. In

Alternative B and Alternative D, in Step 1, the UE is affirmativelyinformed of the disaster condition in the PLMN Y. In all Alternatives ofStep 1, the UE becomes aware that the PLMN X is available for disasterroaming for the UE when the UE receives the disaster roaming PLMN listin Step 2.

Step 4: As the UE determined that PLMN Y has a “disaster condition” andthat PLMN X is available for disaster roaming, the UE attempts toregister with PLMN X. In one embodiment, this is done despite the factthat the UE is otherwise not able to use PLMN X (e.g., PLMN X is inforbidden PLMN list of the UE). In one embodiment, the UE attempts toregister with the PLMN X only if there is no other PLMN which isavailable and allowable using non-disaster roaming method of the CBE 114referred to in FIG. 6 . This method may be performed by one or morenetwork nodes that provide the functionality of the CBE 114 describedherein. The method in FIG. 7 includes:

-   -   Step 700: Receiving, in a CBE 114, information about a disaster        condition in a second PLMN in an area of a UE 112;    -   Step 702: Deciding, in the CBE 114, that a first PLMN is to        provide disaster roaming to UEs of the second PLMN in the area;        and    -   Step 704: Instructing the first PLMN to broadcast a PWS message        comprising (a) a disaster roaming PLMN list and (b) a message        identifier set to the disaster-roaming-possible value.

FIG. 8 is a schematic block diagram of a network node 800 according tosome embodiments of the present disclosure. Optional features arerepresented by dashed boxes. The network node 800 may be, for example, aRAN node (also referred to herein as a radio access node) such as e.g. abase station 102 or 106 or a network node that implements all or part ofthe functionality of the base station 102 described herein or a networknode that performs the functionality of some other network entity (e.g.,the CBE 114 or CBC 116) as described herein. As illustrated, the networknode 800 includes a control system 802 that includes one or moreprocessors 804 (e.g., Central Processing Units (CPUs), ApplicationSpecific Integrated Circuits (ASICs), Field Programmable Gate Arrays(FPGAs), and/or the like), memory 806, and a network interface 808. Theone or more processors 804 are also referred to herein as processingcircuitry. In addition, if the network node 800 is a radio access node,the network node 800 may include one or more radio units 810 that eachincludes one or more transmitters 812 and one or more receivers 814coupled to one or more antennas 816. The radio units 810 may be referredto or be part of radio interface circuitry. In some embodiments, theradio unit(s) 810 is external to the control system 802 and connected tothe control system 802 via, e.g., a wired connection (e.g., an opticalcable). However, in some other embodiments, the radio unit(s) 810 andpotentially the antenna(s) 816 are integrated together with the controlsystem 802. The one or more processors 804 operate to provide one ormore functions of the network node 800 as described herein (e.g., one ormore functions of a RAN node or other network entity such as, e.g., theCBC 116 or the CBE 114 as described herein). In some embodiments, thefunction(s) are implemented in software that is stored, e.g., in thememory 806 and executed by the one or more processors 804.

FIG. 9 is a schematic block diagram that illustrates a virtualizedembodiment of the network node 800 according to some embodiments of thepresent disclosure. Again, optional features are represented by dashedboxes. As used herein, a “virtualized” network node is an implementationof the network node 800 in which at least a portion of the functionalityof the network node 800 is implemented as a virtual component(s) (e.g.,via a virtual machine(s) executing on a physical processing node(s) in anetwork(s)). As illustrated, in this example, the network node 800includes one or more processing nodes 900 coupled to or included as partof a network(s) 902. Each processing node 900 includes one or moreprocessors 904 (e.g., CPUs, ASICs, FPGAs, and/or the like), memory 906,and a network interface 908. If the network node 800 is a radio accessnode, the network node 800 may include the control system 802 and/or theone or more radio units 810, as described above. The control system 802may be connected to the radio unit(s) 810 via, for example, an opticalcable or the like. If present, the control system 802 or the radiounit(s) are connected to the processing node(s) 900 via the network 902.

In this example, functions 910 of the network node 800 described hereinare implemented at the one or more processing nodes 900 or distributedacross the one or more processing nodes 900 and the control system 802and/or the radio unit(s) 810 in any desired manner. In some particularembodiments, some or all of the functions 910 of the network node 800described herein are implemented as virtual components executed by oneor more virtual machines implemented in a virtual environment(s) hostedby the processing node(s) 900. As will be appreciated by one of ordinaryskill in the art, additional signaling or communication between theprocessing node(s) 900 and the control system 802 is used in order tocarry out at least some of the desired functions 910. Notably, in someembodiments, the control system 802 may not be included, in which casethe radio unit(s) 810 communicate directly with the processing node(s)900 via an appropriate network interface(s).

In some embodiments, a computer program including instructions which,when executed by at least one processor, causes the at least oneprocessor to carry out the functionality of the network node 800 or anode (e.g., a processing node 900) implementing one or more of thefunctions 910 of the network node 800 in a virtual environment accordingto any of the embodiments described herein is provided. In someembodiments, a carrier comprising the aforementioned computer programproduct is provided. The carrier is one of an electronic signal, anoptical signal, a radio signal, or a computer readable storage medium(e.g., a non-transitory computer readable medium such as memory).

FIG. 10 is a schematic block diagram of the network node 800 accordingto some other embodiments of the present disclosure. The network node800 includes one or more modules 1000, each of which is implemented insoftware. The module(s) 1000 provide the functionality of the networknode 800 described herein. This discussion is equally applicable to theprocessing node 900 of FIG. 9 where the modules 1000 may be implementedat one of the processing nodes 900 or distributed across multipleprocessing nodes 900 and/or distributed across the processing node(s)900 and the control system 802.

FIG. 11 is a schematic block diagram of a wireless communication device1100 according to some embodiments of the present disclosure. Thewireless communication device 1100 may be, e.g., the wirelesscommunication device 112 or UE described above. As illustrated, thewireless communication device 1100 includes one or more processors 1102(e.g., CPUs, ASICs, FPGAs, and/or the like), memory 1104, and one ormore transceivers 1106 each including one or more transmitters 1108 andone or more receivers 1110 coupled to one or more antennas 1112. Thetransceiver(s) 1106 includes radio-front end circuitry connected to theantenna(s) 1112 that is configured to condition signals communicatedbetween the antenna(s) 1112 and the processor(s) 1102, as will beappreciated by on of ordinary skill in the art. The processors 1102 arealso referred to herein as processing circuitry. The transceivers 1106are also referred to herein as radio circuitry. In some embodiments, thefunctionality of the wireless communication device 1100 described above(e.g., one or more functions of the wireless communication device 112 orUE described above) may be fully or partially implemented in softwarethat is, e.g., stored in the memory 1104 and executed by theprocessor(s) 1102. Note that the wireless communication device 1100 mayinclude additional components not illustrated in FIG. 11 such as, e.g.,one or more user interface components (e.g., an input/output interfaceincluding a display, buttons, a touch screen, a microphone, aspeaker(s), and/or the like and/or any other components for allowinginput of information into the wireless communication device 1100 and/orallowing output of information from the wireless communication device1100), a power supply (e.g., a battery and associated power circuitry),etc.

In some embodiments, a computer program including instructions which,when executed by at least one processor, causes the at least oneprocessor to carry out the functionality of the wireless communicationdevice 1100 according to any of the embodiments described herein isprovided. In some embodiments, a carrier comprising the aforementionedcomputer program product is provided. The carrier is one of anelectronic signal, an optical signal, a radio signal, or a computerreadable storage medium (e.g., a non-transitory computer readable mediumsuch as memory). FIG. 12 is a schematic block diagram of the wirelesscommunication device 1100 according to some other embodiments of thepresent disclosure. The wireless communication device 1100 includes oneor more modules 1200, each of which is implemented in software. Themodule(s) 1200 provide the functionality of the wireless communicationdevice 1100 described herein.

Any appropriate steps, methods, features, functions, or benefitsdisclosed herein may be performed through one or more functional unitsor modules of one or more virtual apparatuses. Each virtual apparatusmay comprise a number of these functional units. These functional unitsmay be implemented via processing circuitry, which may include one ormore microprocessor or microcontrollers, as well as other digitalhardware, which may include Digital Signal Processor (DSPs),special-purpose digital logic, and the like. The processing circuitrymay be configured to execute program code stored in memory, which mayinclude one or several types of memory such as Read Only Memory (ROM),Random Access Memory (RAM), cache memory, flash memory devices, opticalstorage devices, etc. Program code stored in memory includes programinstructions for executing one or more telecommunications and/or datacommunications protocols as well as instructions for carrying out one ormore of the techniques described herein. In some implementations, theprocessing circuitry may be used to cause the respective functional unitto perform corresponding functions according one or more embodiments ofthe present disclosure.

While processes in the figures may show a particular order of operationsperformed by certain embodiments of the present disclosure, it should beunderstood that such order is exemplary (e.g., alternative embodimentsmay perform the operations in a different order, combine certainoperations, overlap certain operations, etc.).

At least some of the following abbreviations may be used in thisdisclosure. If there is an inconsistency between abbreviations,preference should be given to how it is used above. If listed multipletimes below, the first listing should be preferred over any subsequentlisting(s).

-   -   3GPP Third Generation Partnership Project    -   5G Fifth Generation    -   5GC Fifth Generation Core    -   5GMM Fifth Generation System Mobility Management    -   5GS Fifth Generation System    -   AF Application Function    -   AMF Access and Mobility Function    -   AN Access Network    -   ASIC Application Specific Integrated Circuit    -   AUSF Authentication Server Function    -   CBC Cell Broadcast Center    -   CBE Cell Broadcasting Entity    -   CP Control Plane    -   CPU Central Processing Unit    -   DN Data Network    -   DSP Digital Signal Processor    -   eNB Enhanced or Evolved Node B    -   EPS Evolved Packet System    -   E-UTRA Evolved Universal Terrestrial Radio Access    -   FPGA Field Programmable Gate Array    -   gNB New Radio Base Station    -   gNB-CU New Radio Base Station Central Unit    -   gNB-DU New Radio Base Station Distributed Unit    -   HPLMN Home Public Land Mobile Network    -   HSS Home Subscriber Server    -   IMSI International Mobile Subscriber Identity    -   IoT Internet of Things    -   IP Internet Protocol    -   LTE Long Term Evolution    -   MME Mobility Management Entity    -   MTC Machine Type Communication    -   NAS Non-Access Stratum    -   NEF Network Exposure Function    -   NF Network Function    -   NR New Radio    -   NRF Network Function Repository Function    -   NSSF Network Slice Selection Function    -   O&AM Operations and Access Management    -   PC Personal Computer    -   PCF Policy Control Function    -   P-GW Packet Data Network Gateway    -   PLMN Public Land Mobile Network    -   PWS Public Warning System    -   QoS Quality of Service    -   RAM Random Access Memory    -   RAN Radio Access Network    -   ROM Read Only Memory    -   RRH Remote Radio Head    -   RTT Round Trip Time    -   SCEF Service Capability Exposure Function    -   SMF Session Management Function    -   UDM Unified Data Management    -   UE User Equipment    -   UP User Plane    -   UPF User Plane Function

Those skilled in the art will recognize improvements and modificationsto the embodiments of the present disclosure. All such improvements andmodifications are considered within the scope of the concepts disclosedherein.

1-28. (canceled)
 29. A User Equipment, UE, comprising: one or moretransmitters; one or more receivers; and processing circuitry associatedwith the one or more transmitters and the one or more receivers, theprocessing circuitry configured to cause the UE to: receive a disasterroaming PLMN list from the second PLMN, the disaster roaming PLMN listcomprising a PLMN Identifier, ID, of the first PLMN experiencing adisaster condition; determine that a first PLMN is not available due toa disaster condition, based on the disaster roaming PLMN list receivedfrom the second PLMN; determine that a second PLMN is available fordisaster roaming, after receiving the disaster roaming PLMN list fromthe second PLMN; and attempt to register with the second PLMN,responsive to determining that the first PLMN is not available due tothe disaster condition and determining that a second PLMN is availablefor disaster roaming, wherein one or more additional PLMN IDs of one ormore additional PLMNs experiencing a disaster condition.
 30. The UE ofclaim 29, wherein the disaster roaming PLMN list is received in abroadcast on a cell in the second PLMN (PLMN X).
 31. The UE of claim 29,wherein the disaster roaming PLMN list is received in a public warningsystem, PWS, message from a cell in the second PLMN.
 32. The UE of claim31, wherein the PWS message comprises (a) a message identifier set to avalue that indicates that disaster roaming is possible on the secondPLMN (PLMN X) and (b) content that comprises the disaster roaming PLMNlist.
 33. The UE of claim 29, wherein the processing circuitry isfurther configured to cause the UE to determine that the second PLMN isavailable for disaster roaming based on the disaster roaming PLMN list.34. The UE of claim 29, wherein, in order to determine that the firstPLMN is not available due to the disaster condition, the processingcircuitry is further configured to cause the UE to: determine that thereis no available cell of the first PLMN (PLMN Y); and determine that aPLMN Identifier, ID, of the first PLMN is comprised in the disasterroaming PLMN list.
 35. The UE of claim 29, wherein, in order todetermine that the first PLMN is not available due to the disastercondition, the processing circuitry is further configured to cause theUE to: transmit a registration request to the first PLMN; not receive aresponse to the registration request; and determine that a PLMNIdentifier, ID, of the first PLMN is comprised in the disaster roamingPLMN list.
 36. The UE of claim 29, wherein, in order to determine thatthe first PLMN is not available due to a disaster condition, theprocessing circuitry is further configured to cause the UE to: transmita registration request to the first PLMN; receive a rejection of theregistration request comprising an indication of the disaster condition.37. The UE of claim 29, wherein, in order to determine that the firstPLMN is not available due to the disaster condition, the processingcircuitry is further configured to cause the UE to: transmit a servicerequest to the first PLMN; not receive a response to the servicerequest; and determine that a PLMN Identifier, ID, of the first PLMN iscomprised in the disaster roaming PLMN list.
 38. The UE of claim 29,wherein, in order to determine that the first PLMN is not available dueto the disaster condition, the processing circuitry is furtherconfigured to cause the UE to: transmit a service request to the firstPLMN; receive a rejection of the service request comprising anindication of the disaster condition.
 39. The UE of claim 29, wherein,in order to determine that the first PLMN is not available due to thedisaster condition, the processing circuitry is further configured tocause the UE to: camp on a cell of the first PLMN; and receive abroadcast on the cell that comprises information that indicates that adisaster condition exists on the first PLMN.
 40. The UE of claim 29,wherein, in order to determine that the first PLMN is not available dueto a disaster condition, the processing circuitry is further configuredto cause the UE to: transmit a registration request to the first PLMN;and receive a registration reject from the first PLMN including amessage indicating that a disaster condition is identified.
 41. The UEof claim 29, wherein, in order to determine that the first PLMN is notavailable due to the disaster condition, the processing circuitry isfurther configured to cause the UE to: transmit a service request to thefirst PLMN; and receive a service reject from the first PLMN including amessage of indicating that a disaster condition is identified.
 42. TheUE of claim 29, wherein the UE is not otherwise permitted to use thesecond PLMN.
 43. A method performed by a Radio Access Network, RAN, nodeof a second PLMN, the method comprising transmitting a disaster roamingPublic Land Mobile Network, PLMN, list comprising a PLMN Identifier, ID,of a first PLMN experiencing a disaster condition for which the secondPLMN is available to provide a disaster roaming, wherein one or moreadditional PLMN IDs of one or more additional PLMNs experiencing adisaster condition.
 44. The method of claim 43, wherein transmitting thedisaster roaming PLMN list comprises broadcasting information comprisingthe disaster roaming list in a corresponding cell of the second PLMN.45. The method of claim 43, wherein transmitting the disaster roamingPLMN list comprises broadcasting a Public Warning System, PWS, messagecomprising the disaster roaming PLMN list in a corresponding cell of thesecond PLMN.
 46. The method of claim 45, wherein the PWS message furthercomprises a message identifier that is set to a value that indicatesthat the second PLMN is available for the disaster roaming.
 47. Themethod of claim 43, further comprising: receiving a registration requestfrom a User Equipment, UE, that desires to use the second PLMN for thedisaster roaming; and processing the registration request such that theUE is allowed to use the second PLMN.